1. Field of the Invention
This invention relates to a new composition for use as a catalyst or electro-catalyst material.
2. Description of the Related Art
(Note: This application references a number of different publications as indicated throughout the specification by one or more reference numbers within brackets, e.g., [x]. A list of these different publications ordered according to these reference numbers can be found below in the section entitled “References.” Each of these publications is incorporated by reference herein.)
Platinum metal, as a discreet nanoparticle or as a film on a nanoparticle support, is the dominant catalyst material for a wide range of catalytic reactions under extreme conditions; e.g., at high temperatures or under acidic environments. Consider the use of Pt catalysts in the Platforming process, first developed in 1949, which enabled the synthesis of gasoline without the addition of lead to the gasoline. Efforts to make the synthesis of gasoline more green include the development of Pt or PtRe catalysts with higher activity or lower Platinum group metal (PGM) loading. In the modern refinery, the Pt-containing catalysts are regenerated once in a six to twenty four month period. The catalyst can be regenerated perhaps 3 or 4 times before it must be returned to the manufacturer for recycling of the PGM catalyst.
In order to reduce vehicle emissions, better catalysts are needed for catalytic converters. In the state-of-the-art (SOA) 3-way catalytic converter, the Pt-based catalysts simultaneously break down the harmful byproducts present in the hot exhaust streams of automobiles exhausts, including: 1) reduction of nitrous oxides to nitrogen and oxygen; 2) oxidation of carbon monoxide to carbon dioxide; and 3) oxidation of unburned hydrocarbon (HCs), according to the following reaction:2CO+2NO→2CO2+N2 
In a 3-way catalytic converter, the Pt or Pt-alloy particles are placed on a high surface area support that is maintained at high temperatures and Pt-based alloys with greater microstructural stability at these temperatures will improve the converter performance over time.
Fuel cells are widely regarded as an alternative to internal combustion engines, and will play a dominant role in a hydrogen economy as power sources for portable power, transportation, and stationary power applications. However, to meet the future requirements outlined by the US Department of Energy, a new class of catalytic materials is required to improve the performance of electrodes used in advanced fuel cell applications [1]. As such, extensive government and industrial research has been performed in an attempt to commercialize fuel cells. In SOA polymer electrolyte membrane fuel cells (PEMFCs) using an acid polymer electrolyte, platinum (Pt) and platinum group metal (PGM) alloy catalysts are used as the cathode material for the reduction of oxygen, and as the anode material for the oxidation of the hydrogen gas fuel.
In either application, the high cost of Pt is an impediment to their use. A significant amount of research is under way to reduce the Platinum group metal (PGM) content in catalytic converters and fuel cells.
Some challenges limiting the widespread application of PEMFCs, that utilize PGM catalysts are: 1) slow kinetics for oxygen reduction; 2) long-term durability issues manifest by metallurgical effects (e.g., Ostwald particle ripening, and surface area loss due to corrosion); and 3) the high cost of platinum.
The reduced PEMFC durability observed in SOA fuel cell systems is driven in large part by the metallurgical changes in the Pt metal used as the cathode for the oxygen reduction reaction (ORR). During fuel cell operation; grain growth (i.e., Ostwald particle coarsening), corrosion of Pt crystals, and the corrosion/gasification of carbon supports under electrochemical polarization are observed, which collectively result in severe cathode degradation. In addition, the optimal performance of SOA PEMFCs is limited by the sluggish kinetics of the ORR on Pt and its alloys; e.g., a large activation potential (i.e., an over-potential Vover˜300 mV) exists even for the SOA catalysts. In new the alloyed catalysts, such as Pt3Co, the durability of polymer electrolyte cell membrane is reduced due to poor corrosion resistance of the cell electrodes, where Co is corroded from the catalyst surface (cathode), and ultimately crosses over into the membrane [2].
In this application, embodiments of the present invention teach a new class of Pt-based catalyst materials. In the description of the catalyst performance, focus on the use of these materials as the cathode material in a PEMFC, and the results presented show that their performance far exceeds that demonstrated by SOA Pt materials, with a greatly reduced Pt content or Pt loading. However, other applications are also disclosed.